Studies of the anomeric center : mechanism and synthesis

Abstract: This thesis is based on three publications and one appendix and is divided into two parts. The first part is a mechanistic study of the anomerization reaction of both aldo and keto glycosides and the second part is a synthetic study of a unusual type of glycosidic linker found in the lipopolysaccharide core Proteus Mirabilis 0270.The first chapter contains a general introduction to the thesis.The second chapter treats the anomerization reaction of alkyl furanosides both by trapping experiments and kinetics. The conclusion from these studies is that the reaction proceeds via a concerted endo-cyclic C-O bond cleavage.The third chapter concerns the anomerization of alkyl pyranosides by the same techniques as those used in chapter 2. The results from these studies confirm that the reaction proceeds via exo-cyclic C-O bond cleavage.In the fourth chapter the anomerization of methyl fructosides has been investigated by trapping experiments. The outcome of this study is that the anomerization of fructosides occur via exo-cyclic C-O bond cleavage and that the anomerization reaction proceeds faster than ring-interconverison.In the final chapter an analogue of the unusual type of glycosidic linker fond in Proteus Mirabilis 0270 has been synthesised i.e. methyl ((1S)-arabinosyl o-(1Æ4,6))-a-D-galactopyranoside.